Permatex RTV Silicone Guide: Black vs Grey vs Red vs Ultra Copper

Permatex makes multiple RTV (Room Temperature Vulcanizing) silicone sealants, each with different properties for different applications. Choosing the right one makes the difference between a seal that holds and one that fails.

Permatex Ultra Black RTV

Best for: Oil pans, valve covers, timing covers, axle housings

The most popular all-purpose RTV. Sensor-safe (won't damage oxygen sensors). Resistant to motor oil, gear oil, coolant, and fuels. Remains flexible through temperature extremes. Use where gaskets are flanged or where there's relative movement.

Permatex Ultra Grey RTV

Best for: Rigid flanged surfaces, intake manifold-to-head joints

Cures rigid rather than flexible. Sensor-safe. Excellent for joints that need to maintain precise alignment under torque. Higher torque strength than Ultra Black.

Permatex Ultra Red High-Temp RTV

Best for: Exhaust manifolds, catalytic converter flanges, high-heat applications

Rated to 650°F (343°C) continuous and 700°F (371°C) intermittent. Use anywhere standard RTV can't handle the heat. Not for coolant or oil applications.

Permatex Ultra Copper RTV

Best for: Exhaust manifolds, headers, high-temp gasket applications

Rated to 700°F continuous. The copper metallic composition provides excellent heat transfer and exceptional high-temperature performance.

Application Tips

Apply a thin, continuous bead (3mm diameter) to a clean, dry surface. Allow to skin for 20 minutes before assembly. Allow 24 hours cure time before introducing fluids.

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